Effects Of Silencing Of ?-Farnesene Synthase Gene In The Fruit Of 'Fertility' Pear On Terpene Synthesis

Superficial scald is the most serious physiological disease in apples and pears that occurs in low-temperature storage.The oxidation of ?-farnesene is considered to be related to the occurrence of superficial scald,but there is no direct evidence about it.Silencing the ?-farnesene synthase gene by RNA interference technology can obtain fruits that produce little ?-farnesene and the pear can be used to study the relationship between superficial scald and ?-farnesene.In this study,the ‘fertility' pears that silenced ?-farnesene synthase gene were used as the experimental group material.The changes of the substances related to the occurrence of superficial scald in the fruit were mainly analyzed.The main results are as follow:(1)Change in the genomic level,transcription level of perennial ‘fertility' pear fruits and flowers were identified by RT-qPCR and other techniques.The results showed that in perennial transgenic ‘fertility' pear flowers and fruits,effection of gene interference is still stable and the expression level of PcAFS was effectively reduced.Finally,during the low-temperature storage of young fruits,the content of ?-farnesene is effectively reduced,and the content of ?-cubebene is increased in the RNAi strain.In addition,when the fruits stored at low temperature,the expression of some genes in MVA pathway of the RNAi strain flowers was also increased.(2)The RNA-seq result of wild-type and PcAFS silencing ‘fertility' young pears fruit after storage at 0 ? for 45 days indicate that HMGS/HMGR/PMK/MPDC genes in the MVA terpene skeleton synthesis pathway was up-regulated in PcAFS silencing fruits,and squalene synthase genes and squalene oxidase genes in the triterpene and sterol synthesis pathway was also upregulated.(3)22 TPS genes were found in Pyrus communis L genome by the bioinformatics method.Through collinear analysis,22 pairs of collinear TPS genes was found in the Pyrus communis L and Pyrus bretschneideri genome.But some TPS genes have changed their positions.Duplication and variation of some TPS genes occurred after the process of species separation,such as the TPS genes contained on chromosome 12.(4)The transcriptome result indicates that that expression pattern correlation index among 25 differential transcription factors and PcAFS was higher than 0.87.And the most significant up-regulation second metabolism pathway in PcAFS silencing fruit is the phenylpropane and flavonoid synthesis pathway.Then the correlation analysis results of the differential gene and PcMYBPA1 gene showed there is PcMYBPA1 gene which is the most up-regulated gene and related with the gene in phenylpropane and flavonoid synthesis pathway.(5)The study determines the change of volatiles in different subspecies of Pyrus communis L pear after 45 days of storage at 0 ? by GC-MS technology.The results showed that ?-cubebene is different in red and green pear,and the content of ?-cubebene is not affected by ethoxyquinoline treatment.